3. Genus Cypricardia. Pl. [VII].
Animal. As above.
Shell. Obliquely elongated, equivalve, inequilateral; valves striated, not ribbed; distinguished from the Cardita by having three teeth beneath the apices, and a callous lengthened tooth or ridge. Inhabits the coast of Guinea and California. Five living species. Three fossil.
- Cypricardia angulata.
- C. Guinaica.
- C. coralliophaga.
- C. rostrata.
- · · · · ·
- C. Californica.*
4. Genus Hiatella. Pl. [VII].
Animal. Unknown.
Shell. Thin, elongated, subrhomboidal, equivalve, very inequilateral, gaping at its inferior edge, and at its posterior extremity; summit very anterior, and much flexed to the front; hinge formed of a single tooth upon one valve corresponding to an emargination in the opposite valve, or of a small tooth with a cardinal pit upon each valve; ligament exterior and dorsal. Inhabits the British seas. Two species.
- Hiatella Arctica.
- H. biaperta.
5. Genus Isocardia. Pl. [VIII].
Animal. Body very thick: edges of the mantle finely papillaceous, separated inferiorly, and united behind by a transverse band, pierced with two orifices surrounded with radiating papillæ; foot small, compressed, trenchant.